Compounds which are inhibitors of HIV protease are currently being investigated for treatment of HIV infection. Certain HIV protease inhibitors comprise a moiety which is a substituted 2,5-diamino-3-hydroxyhexane. HIV protease inhibitors of particular interest are compounds of the formula 1: ##STR2## wherein n is 0 or 1, R.sub.a and R.sub.b are independently selected from loweralkyl, cycloalkyl, aryl, alkoxyalkyl, thioalkoxyalkyl and heterocyclic, R.sub.1 and R.sub.1a are independently selected from loweralkyl and R.sub.2 and R.sub.2a are independently selected from -C(O)-R.sub.4 -R.sub.5 wherein at each occurrence R.sub.4 is independently selected from O, S and -N(R.sub.6)- wherein R.sub.6 is hydrogen or loweralkyl and at each occurrence R.sub.5 is independently selected from benzyl, (thiazolyl)methyl and (pyridyl)methyl; or a pharmaceutically acceptable salt, prodrug or ester thereof. Compounds of formula 1 are disclosed in European Patent Application No. EP0486948, published-May 27, 1992.
A preferred HIV protease inhibitor is a compound of formula 2: ##STR3## or a pharmaceutically acceptable salt, prodrug or ester thereof.
A more preferred HIV protease inhibitor is a compound of the formula 3. ##STR4## or a pharmaceutically acceptable salt, prodrug or ester thereof.